Packet switching equipment wherein the information packaged in packets are communicated with an asynchronous time-division multiplex transmission technique can be utilized in broadband networks or, respectively, integrated services networks. The functioning and the structure of such packet switching equipment as well as their embedding in broadband networks or integrated services networks are known, for example, from the publication "Nachrichtentechnische Zeitschrift NTZ", Vol. 40, pages 572-577, "Asynchrone Zeitvielfach-Ubermittlungstechnik fuer Breitbandnetze" and from the publication "IEEE Journal on Selected Areas in Communications", Vol. 4, No. 8, (1986), pages 1373 through 1380, "Design of an Integrated Service Packet Network" as well as from U.S. Pat. No. 4,491,945. In such a packet switching network, the data of a subscriber terminal equipment connected to the packet switching equipment are fundamentally segmented in a packetizer and are provided with a header. The header at least contains information about the logic channels to be used and about the packet type. A plurality of physical connections in the subscriber line area of packet switching equipment are replaced by a plurality of logical or virtual connections as well that are referred to as logical channels. When a plurality of subscriber terminal equipment are to receive access to a subscriber line, this ensues on the basis of an asynchronous multiplexing means that, for example, can likewise be realized with a multiple access method.
The packets formed in the subscriber terminal equipment are transmitted to the packet switching means via a subscriber line means inserted between the subscriber terminal equipment and the packet switching means. All transmission methods utilized for the communication of digital information are suitable on the subscriber line, particularly for high transmission speeds. The header information are separated in the packet switching means and are interpreted by a central controller arranged in the packet switching equipment. When the communicated packet type is a connection set-up packet, then a virtual connection to the destination subscriber terminal equipment is constructed with the assistance of the destination address information recited in the message field of this packet and with the assistance of the central controller. This means that a logical or, respectively, virtual connection is set up via the switching equipment arranged in the packet switching means. The virtual connection can be conducted via further packet switching equipment beyond the packet switching equipment to which the originating subscriber terminal equipment is connected. For this purpose, a suitable call set-up procedure is to be provided between the packet switching equipment. The other packets to be communicated via a virtual connection are recognized in the packet switching equipment in accord with the information recited in the header and are communicated via the respective virtual connection.
The "asynchronous time-division multiplex transmission technique" provided for the packet switching equipment--also known as "fast packet switching", "asynchronous transfer mode, ATM" and "asynchronous time division technique, ATD"--is a matter of a packet-oriented switching method wherein the error elimination procedures and the flow control known from CCITT Recommendation X.25 are not provided. An error elimination method for the header information, however, seems meaningful. Further error-handling procedures as well as the flow control are left up to the end-to-end protocols that sequence between the subscriber terminal equipment.
It is also known to realize broadband networks on the basis of annular networks. Standardized access methods are thereby utilized to an increasing degree--particularly at high transmission speeds. Such a ring access method is represented, for example, by the standardized token access method of ANSI X3, T9.5, "fiber distributed data interface (FDDI)", token ring access control (MAC). This method assumes a ring-shaped network that is composed of serially connected subscriber terminal equipment. The information are serially communicated via the annular network in the packet mode. Each of the subscriber terminal equipment is equipped with a reception means and with a transmission means. A ring access means is inserted therebetween, the ring access procedures set forth above being realized therein. A subscriber terminal equipment accesses the annular network with the assistance of the ring access procedure.
The invention achieves the object of combining the two systems in a mutually supplementary and supporting way.